Method and tool for hot forming a metal workpiece

ABSTRACT

The invention relates to a hot forming tool ( 1, 101, 201, 301 ) for hot forming a metal workpiece ( 4, 204 ), having at least two dies ( 2, 3; 202, 203; 202, 303 ) which may be moved relative to one another for forming the workpiece ( 4, 204 ), and having a cooling device ( 5 ) by means of which the workpiece ( 4, 204 ) may be cooled in the hot forming tool ( 1, 101, 201, 301 ) from a first, higher temperature to a second, lower temperature. To improve the hot forming tool ( 1, 101, 201, 301 ), it is provided that the hot forming tool ( 1, 101, 201, 301 ) is equipped with a separating device ( 10, 210, 310 ) by means of which a separating operation may be carried out on a workpiece ( 4, 204 ) present in the hot forming tool ( 1, 101, 201, 301 ). The invention further relates to a method for hot forming.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from German Patent Application SerialNo. 10 2006 040 224.3 filed on Aug. 28, 2006, entitled “Verfahren andWerkzeug zum Warmumformen eines Metallwerkstücks” (Method And Tool ForHot Forming A Metal Workpiece), which is incorporated herein byreference for all purposes.

FIELD OF THE INVENTION

The present invention relates to a method and a tool for hot forming ofmetal work pieces.

BACKGROUND OF THE INVENTION

For such a known generic forming tool, a metal workpiece heated to theaustenitizing temperature is formed. The forming tool has a coolingdevice by means of which the workpiece present in the forming tool isquenched in order to convert the austenitic structure to a martensiticstructure, i.e., to harden the workpiece. In this regard it is importantto maintain a specific variation of the temperature of the workpieceover time to achieve the desired hardness and type of martensiticstructure. In particular, a minimum cooling rate is necessary. On theother hand, the cooling must be coordinated with the forming. If theworkpiece hardens too soon, the forming is adversely affected.

The workpiece is held in the forming tool until it has cooled to atemperature of approximately 100° C. This ensures that the workpiece hassufficiently cooled and has dimensions that essentially correspond toits final dimensions.

The workpiece is then delivered to further machining steps in which itsouter contour is trimmed, for example using a laser or plasma cuttingunit.

JP 2005-248253 A relates to a method for hot forming of steel material.The steel material is heated and positioned between an upper die and alower die. The hot forming is then performed. The closed dies togetherwith the workpiece present therein are moved downward relative to apunch and a trimming edge in order to punch the workpiece and trim itsedge. The punch cooperates with a punch recess in the upper die, and thetrimming edge cooperates with a side edge of said die. The punch and thetrimming edge are fixed to a stationary platform.

US 2002/0113041 A1 discloses various forming devices. One of theseforming devices also has a punching die which is provided in an upperdie and cooperates with a corresponding recess in a lower die. Aworkpiece is placed between the opened dies. The dies are then broughttogether, thereby forming the workpiece. When the dies are completelybrought together they securely hold the workpiece in position, thusallowing punching to be carried out using the punching die.

WO 99/26740 relates to fine-edge blanking of a semihot formed workpiece.In a first process area punching material is provided, in a secondprocess area is preheated, and in a third process area is heated to asemihot forming temperature and is formed. Fine-edge blanking of thecompletely formed part is carried out in a fourth process area.

DE 10 2004 019 693 A1 relates to a method in which a workpiece is heatedto a temperature of approximately 950° C., and is then hot formed usinga first and a second die. After the dies are closed, the workpieceremains for a period of time between the closed dies in order to cool.During the holding period the workpiece is punched, using a punchprovided in the lower die.

SUMMARY OF THE INVENTION

The invention relates to a method for hot forming a metal workpiece, inwhich the workpiece is first formed in a forming tool at a first, highertemperature, and reaches a second, lower temperature at which thematerial of the workpiece has a much higher strength than at the firsttemperature. The invention further relates to a forming tool for thispurpose.

The object of the present invention is to improve a method for hotforming of a metal workpiece in such a way that the workpiece is formedin the simplest manner possible and undergoes a separating operation,and to provide a corresponding device for this purpose.

The object is achieved according to the invention by use of a method forhot forming of a metal workpiece, having the features of claim 1.

This enables the separating operation to be performed directly on theworkpiece in the forming tool. It is even possible to provide goodcoordination of the forming and the separating operation as a functionof time, also taking the cooling into consideration. The integratedmethod of forming and separation also allows high production accuracy tobe achieved.

Because the separating operation is carried out before the workpiecereaches the second temperature, mechanical separating agents may also besatisfactorily used. Before it reaches the second temperature theworkpiece still has a much lower strength; i.e., the wear on mechanicalseparating agents is low.

Separation may be carried out by means of a relative motion between aworkpiece holder and a die for the hot forming tool. The separatingoperation may advantageously be performed using the workpiece holder.

Alternatively or additionally, separation may be performed directly bybringing together two dies for the forming tool. In this mannerseparation and forming are carried out in a single integrated operationas a result of bringing the dies together.

The structure of the workpiece may advantageously be converted duringthe transition from the first to the second temperature. The structuralconversion allows the higher strength to be achieved in a particularlysatisfactory manner.

The structure may preferably be converted from an austinitic to amartenistic structure. In this manner hardening of the workpiece isintegrated into the method.

The separation may advantageously be completed before the structure hasbeen converted. The separating operation may thus be carried out beforecomplete structural conversion has taken place, and the workpiece, whichis still fairly soft, may be separated with low wear.

The separation may be carried out in a particularly advantageous mannerin a temperature range of approximately 350° C. to 500° C. In thistemperature range the workpiece is still sufficiently soft. Mechanicalseparating agents may be used in this temperature range with a goodservice life.

Separation may preferably be carried out directly after the forming iscompleted. This results in high accuracy, since the forming no longeralters the geometry of the workpiece.

Separation may particularly preferably be carried out toward the end ofthe forming operation. At this point the workpiece is sufficientlyformed, so that high accuracy may still be achieved when separation isperformed.

The separation may particularly preferably be performed for a residualpath of dies for the forming tool of approximately one to three timesthe material thickness of the workpiece, preferably for a residual pathof approximately twice the material thickness of the workpiece. Thisachieves high accuracy for a separation carried out toward the end ofthe forming operation.

In a particularly advantageously manner, after separation a region ofthe workpiece adjacent to the separation point may be displaced in thedirection of the region of the dies for the forming tool. The intendedfinal contour is thus achieved by moving the workpiece into the regionof the dies.

The workpiece holder may advantageously be moved relative to a firstdie, which before the separation essentially maintains its relativeposition with respect to the workpiece holder. In this manner the dieand the workpiece holder are essentially able to maintain their positionrelative to one another, and during separation the separating operationoccurs as a result of the relative motion.

The workpiece holder may particularly preferably be moved relative tothe first die after the first die has completed its motion relative to asecond die. Thus, for example, the workpiece holder could continue tomove after the first die has met the second die, thus carrying out theseparating operation.

The first die may preferably be moved relative to the workpiece holderafter the workpiece holder has completed its motion relative to a seconddie. For example, the first die could continue moving toward the seconddie after the relative motion of the workpiece holder with respect tothe second die has been stopped, thus carrying out the separatingoperation.

The dies may advantageously have cutting elements for a separatingdevice, which during the separation are held in their relative positionwith respect to the shaping contour of the respective die. Thus, theintegrated separation and forming operation is possible by means of amechanically simple motion of the dies, which perform the separationwith the assistance of their cutting elements.

In one refinement of the invention, during the separation a first moldedpart of a die may be moved relative to a second molded part of said die.Thus, the separating operation may be carried out by means of a relativemotion of the molded parts. In one particular design, a region of theworkpiece associated with one of the molded parts may be completelyformed before the separation. High accuracy during separation may beachieved in this manner.

The separating operation may be performed in a particularly advantageousmanner using at least one separating device, which immediately after theseparation is moved back to its position before the separation. Thiskeeps the duration of contact of the separating device with theseparating plane of the workpiece low, thereby limiting the heating ofthe separating device. Not only is the wear caused by heating or thermalexpansion of the separating device reduced, but also jamming of theseparating device and workpiece is counteracted.

The separating operation may be used in a particularly advantageousmanner to produce an edge contour on the workpiece. A projecting lengthremaining from the forming may thus be removed.

The workpiece is preferably punched in the hot forming tool. In thismanner a closed workpiece region is separated from the workpiece.

Punching is advantageously carried out only after the workpiece has beenformed. High accuracy of the punched contour is thus achieved.

The object of the invention is further achieved by use of a hot formingtool for hot forming of a metal workpiece, having the features of Claim19.

It is thus possible to provide the hot forming tool with a separatingdevice, by means of which a separating operation may be carried outdirectly on the workpiece present in the hot forming tool. By using sucha separating device it is even possible to provide good coordination ofthe forming and the separating operation as a function of time, alsotaking cooling into consideration. In addition, high production accuracymay be achieved by using the hot forming tool provided with theseparating device.

At least a portion of the separating device may be provided with aworkpiece holder which secures the workpiece during forming and is ableto move relative to a die, thus allowing a separating operation to becarried out by means of this relative motion. The separating operationmay thus be advantageously performed with the assistance of theworkpiece holder.

Alternatively or additionally, the separating device may have mutuallyassociated cutting elements provided on the dies which perform aseparating operation on the workpiece when the dies are broughttogether. In this manner forming and separation are carried out in asingle integrated operation as a result of the dies coming together.

The workpiece holder may particularly preferably be movable relative toa first die which essentially maintains its relative position withrespect to the workpiece holder until separation is achieved. In thismanner the die and the workpiece holder are essentially able to maintaintheir relative position, and during separation the separating operationoccurs as a result of the relative motion.

The workpiece holder may advantageously be movable relative to a seconddie over a dead center point of the dies in the closed state. Theseparating operation may be carried out, for example, by the workpieceholder continuing its motion relative to the second die while the firstdie no longer moves relative to the second die.

The first die may advantageously be movable relative to a second dieover a dead center point of the workpiece holder with respect to thesecond die. Thus, the first die, for example, could continue its motionrelative to the second die while the workpiece holder rested withrespect to the second die, thus carrying out the separating operation.

Preferably, at least one cutting element may be provided on theworkpiece holder, and at least one cutting element for the separatingdevice may be provided on the die. Thus, a separating operation may becarried out by means of a relative motion of the die and the workpieceholder.

The separating device may advantageously have a punching tool which isconnected to the workpiece holder and is able to move with same. Movingthe workpiece holder causes the punching tool to be moved, thus allowinga separating operation to be performed. It is possible to carry outsimultaneous separating operations with the assistance of the motion ofthe punching tool and the workpiece holder.

The cutting elements may advantageously be fixed in position withrespect to the shaping contour of their respective dies. It is thuspossible to carry out forming and separation by means of a mechanicallysimple motion of the dies, which achieve the separation with assistancefrom the cutting elements.

In one refinement of the invention, a die may have a first molded part,as well as a second molded part which during the separation may be movedrelative to the first molded part. A region of the workpiece associatedwith one of the molded parts may be completely formed before theseparation. High separation accuracy may be achieved in this manner.

It is particularly advantageous for the separating device to have apunching tool. In this manner a closed workpiece region may be separatedfrom the workpiece.

The separating device may advantageously have at least one cuttingelement which contains a Cu—Zr alloy. This imparts high heat strength tothe cutting element, resulting in good wear resistance. In addition, thecutting element has good thermal conductivity. This opens thepossibility for carrying out separation also at temperatures ofapproximately 500° C. to 350° C., for example, with indirect cooling ofthe cutting element.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will now be described inconjunction with the following drawings wherein like numerals representlike elements, and wherein:

FIG. 1 shows a hot forming tool according to a first embodiment of theinvention;

FIG. 2 shows a hot forming tool according to a second embodiment of theinvention;

FIG. 3 shows a hot forming tool according to a third embodiment of theinvention; and

FIG. 4 shows a hot forming tool according to a fourth embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description, the same reference numerals are used foridentical or analogous elements.

The left half of each figure shows a position before the forming, andthe right half of the figure shows a position after forming andseparation.

In the following description, the term “forming” is understood to meanan alteration of the shape of a workpiece under the influence of adeforming tool.

FIG. 1 shows a hot forming tool 1 in a first embodiment of theinvention, having two dies 2, 3 which may be moved relative to oneanother for forming a metal workpiece 4, a cooling device 5, aseparating device 10, and a workpiece holder 12.

By use of the cooling device 5, the metal workpiece 4 in the hot formingtool 1 may be cooled from a first, higher temperature to a second, lowertemperature. The cooling device 5 has cooling lines 8, 9 provided in theregion of shaping surfaces 6, 7 of the dies 2, 3, and has cooling lines27, 28 provided in the region of the separating device 10 and theworkpiece holder 12, through which a coolant is conducted.

Using the separating device 10, a separating operation may be carriedout on the metal workpiece 4 present in the hot forming tool 1. Aportion of the separating device 10 is provided with one of the dies,and is indirectly cooled by the cooling lines 27 provided in thisregion. Another portion of the separating device 10 is provided with theworkpiece holder 12, which secures the metal workpiece during theforming and is able to move relative to the die, and is indirectlycooled by the cooling lines 28 provided in this region.

At least a portion of the separating device may also be provided fordirect cooling using cooling lines.

The workpiece holder 12 in particular has a first holding part 14 and asecond holding part 15, between which the metal workpiece 4 is held. Inthe present embodiment of the invention, the first holding part 14 isprovided with a first cutting element 11 of the separating device 10 andis located next to the first die 2, the workpiece holder 12 beingmovable relative to the first die.

The second die 3 is provided with a second cutting element 13 of theseparating device 10, which corresponds to the first cutting element 11and cooperates with same during the separation. The first cuttingelement 11 is a part of the shaping surface of its die. In the startingposition before the forming, as shown in the left half of FIG. 1, thefirst and second cutting elements are located on opposite sides of themetal workpiece 4.

The separating device 10 also has a punching tool 16 having a thirdcutting element 17. The punching tool 16 is connected to the workpieceholder 12 and is able to move with same. The workpiece holder 12 and thepunching tool 16 are mounted on a shared base plate 18. The base plate18 spans the region of the dies. The first holding part 14 rests againstthe base plate.

When the base plate 18 moves relative to the first die 2, this causesthe first holding part 14 and the punching tool 16 to move relative tothe first die 2. The relative movability of the base plate 18 withrespect to the first die 2 is made possible by a die cushion 19. The diecushion 19 may have spring elements and/or fluidic elements, for examplehydraulic cylinders.

At least one of the cutting elements, in the present embodiment of theinvention all of the cutting elements 11, 13, 17, contain an alloy whichis highly heat-resistant and at the same time has good thermalconductivity. As a result, the cutting element experiences low wear,even at high temperatures, and is able to quickly dissipate absorbedheat. Thus, the cutting element may be sufficiently cooled by indirectcooling. However, the cutting element may also be actively cooled, forexample by incorporating cooling channels and conducting coolant.

The cutting element preferably contains a Cu—Zr alloy.

The function of the hot forming tool 1 in the first embodiment of theinvention is described below.

The metal workpiece 4 is heated to its first temperature, at which ithas reduced strength and increased forming capability. In the presentembodiment of the invention, the first temperature is an austenitizingtemperature. This temperature may be selected, for example, in a rangefrom 900° C. to 950° C.; the metal workpiece may be a boron alloy steel.The workpiece may be annealed for a certain period at the firsttemperature.

The workpiece is then positioned between the cold and actively cooleddies 2, 3, and is clamped between the holding parts 14, 15 of theworkpiece holder 12. The second holding part 15 is opened and closed byan actuator 38 which may be operated hydraulically and/or by elasticforce. The workpiece holder assumes the complete holding function forthe workpiece.

Bringing together the dies 2, 3 causes the workpiece to be formed, whichin the present case is a deep-drawing operation. The base plate18—together with the workpiece holder 12 and the punching tool16—maintains its relative position with respect to the first die 2 untilthe meeting of the dies has reached a dead center point, i.e., the dies2, 3 are in the closed state. The forming of the workpiece 4 is completewhen the dead center point has been reached.

The base plate 18 is then moved relative to the first die 2 in thedirection of the second die, i.e., toward the workpiece 4. This causesthe workpiece holder 12 to move relative to the first die, and as aresult of this relative motion the first and second cutting elements 11,13 perform a separating operation, by means of which an edge region 24of the workpiece 4 is separated. At the same time, the punching tool 16is moved relative to the first die 2, namely, through an opening 20 inthe first die 2, until it passes into a corresponding counteropening 21in the second die 3. As a result, a punched piece 25 is separated fromthe metal workpiece and is removed through the counteropening 21.

High accuracy in the separation is achieved by separation after theforming is completed.

The forming and separation are performed continuously. In particular,the separation is essentially completed before the workpiece reaches asecond, lower temperature at which its material has a much higherstrength than at the first temperature. In the present embodiment of theinvention, the second temperature is a martensitic temperature. Themetal workpiece is quenched by the cooling device 5 in the hot formingtool, thereby converting its austenitic structure to a martensiticstructure during the transition from the first to the secondtemperature. The separation may be carried out, for example, in atemperature range of the workpiece 4 of approximately 500° C. to 350° C.

The right half of FIG. 1 shows the state of the hot forming tool 1directly after the separation. Immediately afterwards, the base plate 18is pulled back relative to the first die 2 along the cutting path,returning to its position before the separation. This causes the firstand third cutting elements 11, 16 to be brought out of contact with therespective separating planes of the workpiece, and the introduction ofheat from the separating planes is ended. The thermal expansion of theworkpiece 4 is decoupled in particular from the cutting element 16, thuscounteracting jamming.

The workpiece remains for a period of time in the hot forming tool untilit has reached a temperature of approximately 100° C. to 150° C. Theworkpiece 4 continues to be held under pressure between the first die 2and the second die 3.

The thermal shrinkage of the workpiece between the time of separationand the removal from the hot forming tool must be taken into account inthe dimensioning of the forming tool. Since the dies remain closed untilthe workpiece is removed, the trimmed edge of the workpiece migratesinward along the cross section of the workpiece. This migration may beseveral millimeters, depending on the geometry of the parts. For thisreason, the dies 2, 3 must have a fairly large design to take intoaccount migration of the trimmed edges of the workpiece. That is to say,the workpiece achieves its final dimensions essentially when it reachesits intended removal temperature.

The cycle time for forming with separation is essentially the same asthe cycle time for forming without separation.

Despite the trimming performed in the forming tool, the trimmed edge ofthe workpiece is just as satisfactory as a cut edge obtained byseparation using a trimming unit that is separate from the hot formingtool.

FIG. 2 shows a hot forming tool 101 in a second embodiment of theinvention. The differences of the second embodiment of the inventionwith respect to the first embodiment of the invention are describedbelow.

In contrast to the first embodiment of the invention, in the secondembodiment the workpiece holder 12 for the hot forming tool 101 is movedrelative to the first die 2 toward the end of the forming operation,i.e., before the forming is completed. Thus, separation is carried outtoward the end of the forming operation. The relative motion, i.e., theseparation, occurs for a residual path of the meeting dies which isapproximately two to three times the material thickness of the metalworkpiece 4, preferably for a residual path of approximately thematerial thickness of the metal workpiece plus approximately 1 mm. Afterthe separation, a region of the workpiece adjacent to the separationpoint is displaced farther in the direction of the region of the dies.However, high accuracy is still achieved for the separation.

As a result of starting the separation earlier, not only is the formingand separation process completed sooner, but also the workpiece ishotter at the time of separation. On the other hand, separation may alsobe carried out when the metal workpiece has already reached its secondtemperature upon completion of the forming.

In the present embodiment of the invention, the preferred relativemotion of the workpiece holder 12 with respect to the first die 2 occurswith the assistance of a stop device 130 and a motion buffer 129 betweenthe base plate 18 and the workpiece holder 12, i.e., between the firstdie 2 and the workpiece holder 12. The motion buffer 129 may be operatedhydraulically and/or by elastic force.

When the dies are brought together, the workpiece holder 12 and thefirst die 2 initially maintain their relative position. Toward the endof the forming, with assistance from a stop device 130 the workpieceholder 12, previously moved together with the first die 2, is preventedfrom further motion relative to the second die 3, i.e., reaches a deadcenter point with respect to the second die 3. With yielding of themotion buffer 129, the first die undergoes further motion relative tothe second die until a shared dead center point is reached; i.e., thedies have come together and the workpiece is completely formed.

In contrast to the first embodiment of the invention, in the secondembodiment of the invention the first cutting element 11 is provided onthe second holding part 15, and the second cutting element 13corresponding thereto is provided on the first die 2. As shown in FIG.2, the cooling lines 27, 28 are correspondingly positioned.

A further difference from the first invention lies in the fact that thepunching tool 16 is no longer provided directly on the base plate 18;instead, with assistance from a separate actuator 131 the punching toolis supported on the base plate so as to be movable relative thereto.This allows separation using the punching tool 16 to be carried outindependently from a separation using the workpiece holder 12. This mayalso occur at a different time than the separation using the workpieceholder 12, for example as in the first embodiment after the forming iscompletely ended.

FIG. 3 shows a hot forming tool 201 in a third embodiment of theinvention. The differences of the third embodiment of the invention withrespect to the first and second embodiments are described below.

In the third embodiment of the invention, the separating device 210 hasmutually associated first and second cutting elements 240, 241, provideddirectly on the dies 202, 203, which directly carry out a separatingoperation on the workpiece 204 as a result of the dies coming together.The cutting elements 240, 241 maintain their relative position withrespect to their respective dies 202, 203.

However, the cutting elements may still have movable parts.

As shown in FIG. 3, the cooling lines 27, 28 are correspondinglyprovided in the region of the cutting elements 240, 241. Direct coolingis also possible.

The separation using the first and second cutting elements 240, 241 isstarted the same way as in the second embodiment of the invention,toward the end of the forming operation for a residual path of the dies,as previously described.

In the third embodiment of the invention, the first and second cuttingelements 240, 241 are each situated in the middle of the shapingsurfaces 206, 207 of the respective dies 202, 203. That is, afterseparation begins the edge region 224 of the workpiece 204 is alsoformed.

Using the first and second cutting elements 240, 241, separation may becarried out on the workpiece 204 in places, the edge region 224remaining at the inner region 226 of the workpiece. However, the edgeregion 224 may also be completely separated from the inner region 226.

In the third embodiment of the invention, the hot forming tool 201 has aworkpiece holder 212, the first holding part 214 of which is providedwith the first die 202. The second holding part 215 of the workpieceholder is movable relative to the first die 202, the same as for thefirst and second embodiments.

The workpiece holder has a partial holding function for the workpiece.Before the forming, there is a space between the first cutting element240 and the workpiece 204 held by the workpiece holder 212.

For the hot forming tool 201 in the third embodiment of the invention,the punching tool 16 is provided in the same manner as for the secondembodiment of the invention.

The fourth embodiment of the invention is described below with referenceto FIG. 4.

The fourth embodiment of the invention is a refinement of the thirdembodiment of the invention. The hot forming tool 301 has a second diewhich is divided into, a first molded part 350 and a second molded part351. The two molded parts 350, 351 are moved relative to one anotherduring the separation. This relative movability is made possible by adie cushion 360 which is provided so as to connect the molded parts.

For forming of the metal workpiece 204, the two dies 202, 303 movetoward one another. First, the forming is completed between the firstdie and one of the molded parts 350. After reaching the dead centerpoint of its relative motion, the first die 202 and this molded partmove together relative to the second molded part 351, thus carrying outthe separating operation. This procedure has the advantage that highaccuracy is achieved for the separation by means of the relativemovability of the two molded parts, the workpiece as a whole beingcompletely formed when the separation begins.

In the fourth embodiment of the invention, the first die 202 travelstogether with the first, inner molded part 350 until the shared deadcenter point is reached. The second, outer molded part 351 has a secondcutting element 341 which corresponds to the first cutting element 240of the first die. This second cutting element performs the separationwhen the first die 202 and the first molded part 350 move togetherrelative to the second molded part 351.

At least one of the cutting elements, in the present case the firstcutting element 240, may have a holding function, in particular duringthe separation, as shown in FIG. 4. This cutting element presses theworkpiece 204 against the inner molded part 350.

What is claimed is:
 1. A hot forming tool for hot forming a metalworkpiece, comprising at least two dies which may be moved relative toone another for forming the workpiece, and having a cooling device bymeans of which the workpiece may be cooled in the hot forming tool froma first, higher temperature to a second, lower temperature, whereby thehot forming tool is provided with a separating device by means of whicha separation can be carried out on a workpiece present in the hotforming tool before the workpiece reaches the second, lower temperature,wherein at least a portion of the separating device is provided with aworkpiece holder which holds the workpiece during the forming operationand is movable relative to at least one of the dies, whereby theseparation step can be carried out by means of this relative motion. 2.The hot forming tool according to claim 1, wherein the workpiece holderis moveable relative to a first one of the dies, which until theseparation essentially maintains its relative position with respect tothe workpiece holder.
 3. The hot forming tool according to claim 2,wherein the workpiece holder includes a first holding part located nextto the first die and a second holding part located next to a second oneof the dies, and both the first holding part and the second holding partare moveable relative to the first die and the second die over a deadcenter point of the dies in the closed state.
 4. The hot forming toolaccording to claim 3, wherein a punching tool is disposed along thefirst die opposite the workpiece holder and is connected to the firstholding part by a baseplate and moves with the first holding part. 5.The hot forming tool according to claim 3 wherein, a punching tool isdisposed along the first die opposite the first holding part and movesrelative to the first holding part and the first die.
 6. The hot formingtool according to claim 2, wherein the first die is moveable relative toa second one of the dies over a dead center point of the workpieceholder with respect to the second die.
 7. The hot forming tool accordingto claim 1, wherein the separation device includes at least one cuttingelement provided on the workpiece holder, and at least one cuttingelement provided on at least one of the dies for performing theseparation on the workpiece.
 8. The hot forming tool according to claim7, wherein the cutting elements are fixed in position with respect to ashaping contour of their respective workpiece holder and die.
 9. The hotforming tool according to claim 1, wherein the separating device has apunching tool which is connected to one of the dies and is moveable withthe same.
 10. The hot forming tool according to claim 1, wherein atleast one of the die has a first molded part, as well as a second moldedpart, wherein the workpiece holder and the first molded part aremoveable relative to the second molded part.
 11. The hot forming toolaccording to claim 1, wherein the separating device has a punching tool.12. The hot forming tool according to claim 1, wherein the separatingdevice has at least one cutting element which contains a Cu—Zr alloy.13. The hot forming tool according to claim 1, wherein the workpieceholder includes a first holding part and a second holding part forengaging and holding the workpiece between the first holding part andthe second holding part during the forming operating.
 14. The hotforming tool according to claim 13, wherein both the first holding partand the second holding part are movable relative to the dies whileholding the workpiece between the first holding part and the secondholding part.
 15. The hot forming tool of claim 1, wherein the metalworkpiece includes steel.
 16. The hot forming tool of claim 1, whereinthe separating device is disposed along one side of the dies and apunching tool is disposed on the opposite side of the dies, the diesinclude a shaping surface extending from the separating device to thepunching tool, the shaping surface has a dimension designed to form theworkpiece to a predetermined finished dimension, and the dimension ofthe shaping surface is greater than the predetermined finisheddimension.
 17. The hot forming tool of claim 1, wherein the workpieceholder includes a first holding part and a second holding part forholding the workpiece therebetween, each of the holding parts is asingle block, and the separation device includes a cutting elementintegral with one of the holding parts.
 18. A hot forming tool for hotforming a metal workpiece, comprising at least two dies which may bemoved relative to one another for forming the workpiece, and having acooling device by means of which the workpiece may be cooled in the hotforming tool from a first, higher temperature to a second, lowertemperature, whereby the hot forming tool is provided with a separatingdevice by means of which a separation can be carried out on a workpiecepresent in the hot forming tool before the workpiece reaches the second,lower temperature, wherein the separating device is provided by mutuallyassociated cutting elements on the dies which perform a separatingoperation on the workpiece when the dies are brought together.
 19. Thehot forming tool according to claim 18, wherein a first one of the diesincludes a workpiece holder which is moveable relative to a second oneof the dies.
 20. The hot forming tool according to claim 19, wherein theworkpiece holder includes a first holding part located next to the firstdie and a second holding part located next to a second one of the dies,and both the first holding part and the second holding part are moveablerelative to the first die and the second die over a dead center point ofthe dies in the closed state.
 21. The hot forming tool according toclaim 20, wherein a punching tool is disposed along the first dieopposite the first holding part and is connected to the first holdingpart by a baseplate and moves with the first holding part.
 22. The hotforming tool according to claim 20, wherein a punching tool is disposedalong the first die opposite the first holding part and moves relativeto the first holding part and the first die.
 23. The hot forming toolaccording to claim 18, wherein a first one of the dies is moveablerelative to a second one of the dies over a dead center point.
 24. Thehot forming tool according to claim 18, wherein at least one of thecutting elements is provided on each of the dies for together performingthe separation on the workpiece.
 25. The hot forming tool according toclaim 18, wherein the separating device has a punching tool which isconnected to one of the dies and is moveable with the same.
 26. The hotforming tool according to claim 18, wherein the cutting elements arefixed in position with respect to a shaping contour of their respectivedies.
 27. The hot forming tool according to claim 18, wherein at leastone of the dies has a first molded part, as well as a second molded,wherein the workpiece holder and the first molded part are moveablerelative to the second molded part.
 28. The hot forming tool accordingto claim 18, wherein the separating device has a punching tool.
 29. Thehot forming tool according to claim 18, wherein at least one of thecutting elements contains a Cu—Zr alloy.
 30. The hot forming toolaccording to claim 18, wherein at least one of the dies includes aworkpiece holder which holds the workpiece during the forming operation.31. The hot forming tool according to claim 18 including a workpieceholder next to the dies, wherein the workpiece holder includes a firstholding part and a second holding part for engaging and holding theworkpiece between the first holding part and the second holding partduring the forming operating.
 32. The hot forming tool according toclaim 31, wherein both the first holding part and the second holdingpart are movable relative to the dies while holding the workpiecebetween the first holding part and the second holding part.
 33. The hotforming tool of claim 18, wherein the metal workpiece includes steel.34. The hot forming tool of claim 18, wherein the separating device isdisposed along one side of the dies and a punching tool is disposed onthe opposite side of the dies, the dies include a shaping surfaceextending from the separating device to the punching tool, the shapingsurface has a dimension designed to form the workpiece to apredetermined finished dimension, and the dimension of the shapingsurface is greater than the predetermined finished dimension.
 35. Thehot forming tool of claim 18, wherein a first one of the dies isintegral with a workpiece holder, and one of the cutting elements isintegral with the first die.